RUCKUS: You're thinking in terms of a relationship. Conditions for intimacy apply before you become involved in an LTR. These are pre-existing criteria each of us have prior to getting involved - we must at least marginally meet individual conditions for intimacy. The term 'intimacy' as I use it, of course, includes sex, this being an obvious indication of intimate acceptance, but it can also cover kissing, passionate affection, etc. that indicates acceptance as well.
Now to cover your points:
Obviously there are more factors involved in maintaining an LTR than sex (mutual respect, love, intellectual and social compatibility, etc.), but again, these are alloted respective priorities in an LTR. Sex is generally the number one priority for men. Would you marry an HB 10 who was a perfect match for you in every respect with the exception that she would never have sex with you? You see, it's easy to say that sex isn't the most important thing to you when you are getting it on fairly regular schedule. It's far eaasier to overlook a person's (male or female) character flaws when you are getting semi-regular sex with them than it is to feel completely affirmed by them when that's the one thing they will not do. Basically when you remove sex from a relationship - either by the woman's choosing or her becoming so physically unattractive that he cannot become aroused - what's in it for the guy? There's no motivational reinforcement to embody her prerequisites for intimacy when he can be absolutely certain that her intimacy will never be reciprocated.
Guy's intrinsically understand this. How frustrating would it be to endure all of the responsibilities an LTR/Marriage with a beautiful woman who simply wasn't sexually accessible? You'd probably never allow yourself to even enter into the circumstance in the first place. Yet even more frustration would be one who once was once accessible and attractive who did find you acceptable for intimacy, but becomes unaccessible.